Caudwell Xtreme Everest is a research project coordinated by the UCL Centre for Altitude, Space and Extreme environment medicine (CASE) - doctors and scientists studying human systems stretched to breaking point in extreme environments to increase our understanding of critically ill patients.

The group placed a research team on the summit of Mount Everest in May 2007 and made the first ever measurement of the level of oxygen in human blood at 8400m, on the balcony of Everest. This was the centrepiece of an extensive and continuing programme of research into hypoxia (low oxygen levels) and human performance at extreme altitude aimed at improving the care of the critically ill and other patients where hypoxia is a fundamental problem.